A case of mistaken identity: Genetic and morphological evidence for the presence of Redeye Bass in the Verde River, Arizona

We report genetic and morphological evidence for the presence of Redeye Bass Micropterus coosae, in the Verde River of Arizona, previously thought to be Smallmouth Bass Micropterus dolomieu. We performed meristic measurements on 15 individuals sampled from the Upper Verde River Wildlife Area, Yavapai County, Arizona. Meristic data for lateral line scales, scales above lateral line, and scales below lateral line were all consistent with Redeye Bass and not Smallmouth Bass. We analyzed mitochondrial and nuclear genetic data to determine if one of the black bass (Genus Micropterus) species historically introduced to the Verde River was Redeye Bass and that they persist in the system. We extracted DNA from fin clips of five individuals for phylogenetic analysis of the NADH dehydrogenase subunit 2 (ND2) mitochondrial gene and for analysis of nuclear DNA using a diagnostic Single Nucleotide Polymorphism (SNP) panel. Results of the ND2 genetic sequencing and phylogenetic analysis indicated that these fish likely originated from native Redeye Bass stock from the Coosa River system of Alabama, Georgia, and Tennessee. Similarly, nuclear SNP data from the five individuals collected from the Verde River aligned with Redeye Bass reference genotypes based on STRUCTURE analysis. These results support the hypothesis that at least one of the introductions of black bass in Arizona’s Verde River founded a previously unrecognized population of Redeye Bass. Further work is needed to determine the extent of the Redeye Bass presence in Arizona, whether Smallmouth Bass are also present in the Verde River system, and if hybridization of Redeye Bass and other black basses is occurring.

Effect of Discharge on Hatching and Growth of Age-0 Black Bass in Two Southeastern U.S. Rivers

We examined the influence of variable discharge on hatching and age-0 growth for fluvial specialist and habitat generalist species of black bass Micropterus spp. in two southeastern U.S. rivers, the Flint River, Georgia (unregulated), and the Tallapoosa River, Alabama (regulated by several hydropower dams). Between 2008 and 2010, we collected 285 Largemouth Bass M. salmoides (generalist) and 254 Shoal Bass M. cataractae (specialist) from two reaches of the Flint River. In 2010–2011, we collected 309 Alabama Bass M. henshalli (generalist) and 216 Redeye Bass M. coosae (specialist) from two regulated reaches and one unregulated reach of the Tallapoosa River. Successful hatching of black bass in both rivers generally occurred from late March to early June when water levels were low and stable. Hatching distributions of all black bass were generally unimodal with little evidence of spawning disruption, except for Alabama Bass in the most-regulated reach of the Tallapoosa River, which appeared to be disrupted by large discharge events. Mean growth of both species in the Flint River varied from 0.64 to 0.82 mm/d across reaches and years; Shoal Bass generally grew faster than Largemouth Bass in all reach–year combinations. Largemouth Bass growth was inversely correlated to discharge variation in one reach, but Shoal Bass growth was not correlated to discharge variation in either reach. Alabama Bass and Redeye Bass growth rates in the Tallapoosa River were similar to rates observed for congeners in the Flint River; Alabama Bass grew faster than Redeye Bass. Growth of both species was inversely related to discharge variation in five of six reach–species combinations; the only exception was for Redeye Bass in the less-regulated reach. Results from this study suggest that variable discharge has less influence on successful reproduction of black bass than was reported for other fishes, but growth may be more affected by discharges resulting from anthropogenic sources than those associated with the natural regime.

Evidence Dorsal Spine Removal is Nonlethal and Unharmful for Largemouth Bass in Florida

Largemouth Bass Micropterus salmoides, Florida Bass M. floridanus, and their intergrade are socially and economically valuable sport fish. In the southeastern United States, it is customary to age black bass (Micropterus) spp. using sagittal otoliths which requires killing the fish. Presently, fisheries managers and black bass anglers show reluctance to sacrifice large individuals. Development of a nonlethal ageing technique would not only allay concerns of sacrificing large black bass, but it could offer a pathway for new research, management, and conservation. We excised dorsal spines III–V from Largemouth Bass in Florida varying from 30–57 cm total length to evaluate the effects of the procedure on survival over 35 days. No mortalities were observed for fish with excised dorsal spines, and experiment-wide survival was 0.94 (0.87–1.00; 95% confidence interval). No significant differences in survival, weight change, or incidence of external injuries were observed between control and excised fish. The areas of spine excision healed with no visible infection or inflammation at the conclusion of the experiment. Therefore, dorsal spine removal offers managers a nonlethal option for collecting ageing structures of adult Largemouth Bass in Florida, including large individuals, and this result likely extends to other Micropterus spp. as well.